Attempting to overclock your new cpu without a proper cooler (which is a minor increase in price considering you are upgrading mobo and cpu) is truly a horrible idea. Everyone's case flow is different, and the same goes for different cpus, none are the same when overclocked. To not invest a further 20bucks on your part for your new upgrade (if you plan to overclock) to get a decent cpu cooler would be foolish. #1 rule in overclocking, get rid of stock cooling. If you choose to do thermal damage or possibly just fry your chip then go ahead, but I highly suggest being proactive in your investment and not risking your hardware unnecessarily.
EDIT: Also, unless a poster is giving you screenshots there is no proof where they ran their cpu. I've seen many people on Tom's and OCN that do damage to their FX cpus because they thought they'd overclock with a stock cooler.